Crystal structure of Septin GTPase domain from Chlamydomonas reinhardtii

Experimental Data Snapshot

  • Resolution: 2.04 Å
  • R-Value Free: 0.232 
  • R-Value Work: 0.195 
  • R-Value Observed: 0.196 

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Filaments and fingers: Novel structural aspects of the single septin from Chlamydomonas reinhardtii.

Pinto, A.P.A.Pereira, H.M.Zeraik, A.E.Ciol, H.Ferreira, F.M.Brandao-Neto, J.DeMarco, R.Navarro, M.V.A.S.Risi, C.Galkin, V.E.Garratt, R.C.Araujo, A.P.U.

(2017) J Biol Chem 292: 10899-10911

  • DOI: https://doi.org/10.1074/jbc.M116.762229
  • Primary Citation of Related Structures:  

  • PubMed Abstract: 

    Septins are filament-forming GTP-binding proteins involved in many essential cellular events related to cytoskeletal dynamics and maintenance. Septins can self-assemble into heterocomplexes, which polymerize into highly organized, cell membrane-interacting filaments. The number of septin genes varies among organisms, and although their structure and function have been thoroughly studied in opisthokonts (including animals and fungi), no structural studies have been reported for other organisms. This makes the single septin from Chlamydomonas (CrSEPT) a particularly attractive model for investigating whether functional homopolymeric septin filaments also exist. CrSEPT was detected at the base of the flagella in Chlamydomonas , suggesting that CrSEPT is involved in the formation of a membrane-diffusion barrier. Using transmission electron microscopy, we observed that recombinant CrSEPT forms long filaments with dimensions comparable with those of the canonical structure described for opisthokonts. The GTP-binding domain of CrSEPT purified as a nucleotide-free monomer that hydrolyzes GTP and readily binds its analog guanosine 5'-3- O -(thio)triphosphate. We also found that upon nucleotide binding, CrSEPT formed dimers that were stabilized by an interface involving the ligand (G-interface). Across this interface, one monomer supplied a catalytic arginine to the opposing subunit, greatly accelerating the rate of GTP hydrolysis. This is the first report of an arginine finger observed in a septin and suggests that CrSEPT may act as its own GTP-activating protein. The finger is conserved in all algal septin sequences, suggesting a possible correlation between the ability to form homopolymeric filaments and the accelerated rate of hydrolysis that it provides.

  • Organizational Affiliation

    From the Instituto de Física de São Carlos, Universidade de São Paulo, CEP: 13563-120, São Carlos, SP, Brazil.

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
Septin-like protein
A, B
308Chlamydomonas reinhardtiiMutation(s): 0 
Gene Names: SEP1CHLREDRAFT_148151
Find proteins for A8IYS5 (Chlamydomonas reinhardtii)
Explore A8IYS5 
Go to UniProtKB:  A8IYS5
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupA8IYS5
Sequence Annotations
  • Reference Sequence
Small Molecules
Modified Residues  1 Unique
IDChains TypeFormula2D DiagramParent
Query on MSE
A, B
Binding Affinity Annotations 
IDSourceBinding Affinity
GSP Binding MOAD:  5IRR Kd: 5400 (nM) from 1 assay(s)
Experimental Data & Validation

Experimental Data

  • Resolution: 2.04 Å
  • R-Value Free: 0.232 
  • R-Value Work: 0.195 
  • R-Value Observed: 0.196 
  • Space Group: C 1 2 1
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 177.58α = 90
b = 39.41β = 118.5
c = 130.9γ = 90
Software Package:
Software NamePurpose
xia2data scaling
PDB_EXTRACTdata extraction
xia2data reduction

Structure Validation

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Ligand Structure Quality Assessment 

Entry History & Funding Information

Deposition Data

Funding OrganizationLocationGrant Number
Sao Paulo Research Foundation (FAPESP)Brazil2011/10152-7

Revision History  (Full details and data files)

  • Version 1.0: 2017-04-26
    Type: Initial release
  • Version 1.1: 2017-05-24
    Changes: Database references
  • Version 1.2: 2017-07-12
    Changes: Database references
  • Version 1.3: 2017-11-01
    Changes: Author supporting evidence
  • Version 1.4: 2019-04-17
    Changes: Author supporting evidence, Data collection
  • Version 1.5: 2020-01-01
    Changes: Author supporting evidence